The following invention relates to a shoe for an impeller-type rock-crushing machine.
Impact-type rock-crushing machines have a flat or gently sloping turntable upon which are mounted a plurality of impeller blades or shoes. Rock is dropped onto the center of the turntable as it is spinning and the centrifugal force of the spinning table forces the stones outwardly where they are thrown by the impeller shoes against anvils located against a cylindrical wall spaced radially outwardly of the turntable. An example of such a rock crushing device is shown in Ackers U.S. Pat. No. 4,090,673.
The continuous nature of the aggregate feed onto the turntable creates a continuous stream of particulate matter which flows across the face of each of the impeller shoes. This continuous stream flow of particulate matter tends to concentrated along a single path across the wear surface of each of the particular shoes. This results in premature wearing of the shoes because the stream flow creates a groove or channel that cuts into the surface of the shoe along a single path rather than wearing down the surface of the shoe evenly. The reason for the wearing down of the surface of the shoe in this manner is not precisely known, but apparently the particulate matter stream behaves as a fluid and thus follows any groove or undulation created in the shoe instead of striking the surface randomly. The fact that the stream of constantly-flowing particulate matter is concentrated in a surface region much narrower than the width of the shoe leads to premature wearing of the shoe and necessitates its frequent replacement.
In the past, shoes for impeller-type rock-crushing machines have been smooth-faced. An example of such a shoe is shown in Warren U.S. Pat. No. 4,174,814. The Warren patent discloses a generally trapezoidal shoe surface having a smooth-faced working surface formed of cast iron. Smooth-surfaced shoes such as the type shown in the Warren patent, however, do not provide any means for breaking up the stream flow of particulate matter which tends to concentrate along a single path and create a wear-valley. Once the wear-valley progresses through the surface of the shoe and begins to reach the base material of the shoe, that is, the support portion of the shoe, the shoe must be replaced in its entirety.
What is needed, therefore, is an impeller blade shoe having means for breaking up the concentrated stream flow of particulate matter so that the shoe wears more evenly, and hence, lasts longer since the material flow across the surface of the shoe will no longer be confined to a single location.